In a very general way, the present invention is a substantial improvement over the Towed Vehicle Electric Brake Control as filed on July 27, 1974 by Rene E. Pittet, et al in the U.S. Pat. application Ser. No. 385,102, now U.S. Pat. No. 3,909,075. The object in the present application is to provide an electronic switching structure which senses deceleration or inertial imbalance; translates the imbalance quantitatively to a pulsed signal of regular width and variable frequency useable at the brakes; and provides a continuously operable short circuit probe preventing injury to the control by reason of external short circuits.
The closest art considered in the preparation of this application by the applicants is represented in the U.S. Pat. No. 3,779,612 to Hans Tschannen which describes an unpulsed brake control structure; U.S. Pat. No. 3,497,266 of Kenneth F. Umpleby directed to an override pulsed system, manually actuated in a multivibrator circuit; U.S. Pat. No. 3,499,689 to Ralph W. Carp, et al which senses wheel deceleration and adjusts air brake response in avoidance of skidding; U.S. Pat. No. 2,032,177 to John W. Logan comprising a fluid pressure brake control using a pendulum - like deceleration sensor physically closing a switch structure; and U.S. Pat. No. 3,486,799 to Herbert Greentree in which proportional deceleration is imparted to the trailer brakes and in which there is a dampened inertial sensor.
The present invention distinguishes over these references in providing a simplified electronic control circuit; a cantilever type dampened beam inertial sensor including a light quantum sensor adjustably calibrated; a constant light source with beam interrupted light emission; and a continuously operative short circuit probe in protection of the control circuit. The probe circuit assures an added safety dimension to users. Further, the use of a constant width variable frequency pulse is believed to assure better trailer braking without danger of lock-up of the brakes as occurs in systems which increase the length of each pulse as is known in the prior art.
Accordingly, the principal object is to provide an improved and safer simplified brake control at lower cost using a simple light emitter such as a bulb as a light source and a light sensitive element and wherein a simple dampened cantilever beam gates the light to the light sensitive transistor on inertial displacement of the beam.
Another object is to utilize a relatively simple power transistor as contrasted to earlier brake controls using complex and expensive Darlington transistors for power conduction, for example.
Another object is to provide a continuous and probing disconnect which senses external short circuits or amperage surges beyond the brake operational threshold and intermittently disables the control until the short circuit is eliminated. Then the control circuit is automatically restored. This probe includes a signal, as for example, a visible light flashing.
Still another object is to improve the brake control by utilizing and generating a brake pulse of constant width but varying frequency.
Other objects including gain adjustment and sensitivity adjustment by tilting the cantilever element will become better understood as the description proceeds.